Percussion hammer drill and method of operating it



Aug.22,1967 y GSJONESJR y 3,336,988

PERCUSSION HAMMER DRILL ANI) METHOD OF OPERATING IT Filed Sept. 18, 1964 2 Sheets-Sheet l FIG. 1.

f INVENTOR I f 39 @ROVER S. JONES JR.

ATTORNEY ug. 22, 967 G. s. JONES, JR

PERCUSSION HAMMER DRILL AND METHOD OF OPERATING IT 2 sheets-sheei` Filed Sept. 18, 1964 INVENTOR GROVER s. .10N Es JR.

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ATTORNEY S LL United States Patent O 3,336,988 PERCUSSION HAMMER DRILL AND METHOD OF OPERATING IT Grover Stephen Jones, Jr., 251 Fallsbrook Road, Timonium, Md. 21093 Filed Sept. 18, 1964, Ser. No. 397,539 11 Claims. (Cl. 173-133) This invention relates to drilling devices and it is more particularly concerned with drills which function by irnpact or percussion forces.

Conventional impact or percussion drills comprise generally a solid bar of substantial weight, i.e., a thousand or more pounds, vertically suspended at the end of a rope or cable. The other end of the cable is connected to a winch, and means are provided between the winch and the bar to raise the bar and allow it to drop repeatedly at a given rate in a selected location where the drilling is to be performed. The bar has a bit or cutting tool at its bottom end. When the drill is repeatedly dropped, the impacts of said bit with the surface to be broken accomplish the useful work. Powered machinery acting through the winch repeated-ly reenergizes the drill by lifting it to a proper height for dropping.

The mechanical eiciency of such conventional drilling devices is markedly poor. The energy input is very high compared to the energy actually expended to do useful work. Furthermore, -only a very small percentage of the capacity potentially available through the powered winch is converted to useful work. On each dropping of the bar the potential energy achieved in raising it is spent between the useful work performed by the bit, damping and impact losses that accomplish no useful work, and the energy of rebound which serves only to lower the energy input requirement of the powered machinery in relifting the drill to a proper dropping height.

The general object of the present invention is the provision of an impact or percussion hammer drill having increased eiliciency in comparison with conventional drills.

A specific object is the provision of means in combination with a conventional drilling rig which is effective to increase the mechanical efficiency of the system as a whole.

Another object of the invention is the provision of means in combination with a conventional drilling r-ig for fuller utilization of the potential work capacity available through the powered machinery to increase drilling efliciency.

Still another object of the invention is the provision of 4a drill of the type mentioned having means for absorbing energy normally lost in conventional percussion drills and utilizing the absorbed energy to perform useful work.

A still further object is the provision of a drill of the type mentioned which is rugged, easy to manufacture, and simple to use.

A still further object is the provision of a method of operating a percussion drill to achieve increased eficiency.

These and still further objects, advantages and features of the invention will be apparent from the description which follows in conjunction with the accompanying drawing to which the description refers.

In the drawing:

FIG. l is a side elevational view of a conventional drilling rig, partly broken away, in combination with a percussion hammer drill comprising an embodiment of the invention.

FIG. 2 is a longitudinal sectional view of the embodiment, partly broken away.

FIGS. 3, 4, 5, -6, 7, 8, 9, l and l1 are schematic diagrams illustrating one cycle of operation of the embodiment in accordance with this invention.

Referring to the drawing with more particularity, there 3,336,988 Patented Aug. 22, 1967 ICC is diagrammatically illustrated in FIG. 1 a conventional drilling rig 21 mounted on an ordinary truck 22. The rig 21 comprises a powered winch 23 about which one end of a cable 24 is wound. The cable passes from the winch 23 over a stationary sheave 25, then under a sheave 26 mounted at the end of an oscillating beam 27 and, thence, to the top of a derrick 28 where it passes over a sheave 29 and then vertically downward to the drill device 30. The drill device 30 conventionally operates in casing sections 31, these sections being connected together serially and lowered into the ground as the drilling progresses.

The embodiment illustrated comprises an elongated solid bar 32 of substantial weight, i.e. a thousand pounds or more, to which one end of the cable 24 is directly or indirectly attached in any conventional manner. The bottom of the bar 32 has a recessed section 33 to which the upper end of an imperforate vertical tubular shell 34 is secured and hermetically sealed by shrink fitting or by any other suitable means. To the bottom of the shell 34 there is secured by shrink tting or any other suitable means, the upper recessed end 35 of a bit holder in the form of a socket 36. The socket 36 has an upper end wall 37 and a cylindrical hollow portion 38 between the wall 37 and its lower end.

The bit 39 has a cylindrical portion 40 which is disposed in and which reciprocates in the hollow portion 38. From the upper end of the cylindrical -portion 40 a rod-like stem 41 projects upwardly through a central opening 42 in the wall 37. The upper end of the stem 41 its into a recess 43 of a slide 44. The slide 44 is disposed within the shell 34 above the end wall 37. Between the slide 44 and the lower end of the bar 32 there is disposed a calibrated coil spring 45. The slide 44 has a central stem 49 which extends upwardly on the interior of a portion of the spring. The upper end 50 of the stem 49 is, in the lowermost or protracted position of the slide 44, a predetermined distance from the bottom side 51 of the bar 32 corresponding to the stroke of the slide 44 between its two extreme positions of protraction and retraction.

It is preferred that a fluid seal be provided between the slide 44 and the shell 34, such as the O-ring 52, in the annular groove 53. This form of seal, however, is for illustrative purposes only and is not intended to be restrictive in any way or to limit the type of seal which may be used.

In FIGS. 3 to 11 there is illustrated by means of a series of diagrammatic sketches the action of the embodiment described above. For simplicity, these figures illustrate only four impacts although in actual practice the number of impacts or vibrations will usually exceed four for each cycle of raisin-g and lowering the drill by the rig 21.

v FIG. 3 shows the beginning of a cycle when the drill has been dropped by the hoisting rig 21 from a predetermined -distan and the bit has just impacted on the bottom of the bore. The remaining FIGS. 4 to l1 show the action during the rest of the cycle consisting of four 'impacts per cycle, each cycle consisting of a raising and a lowering of the tool by the rig.

In a conventional solid bar drill of weight W which is dropped in such a manner as to strike the ground with a velocity magnitude w1, the energy Eo immediately preceding impact with the bottom of the bore is given by the formula: f

The ratio of the velocity with which the drill bounces from the bottom of the bore divided by u1 may be termed the coefficient of restitution k and k will yalways be less than unity. In the range of weights to be considered it Esa @www Therefore, the energy delivered to the ground (the energy with which drilling must be accomplished) is given by the formula:

The harder the surface presented by the bottom of the bore the closer the value of k will be to unity. Thus, for very hard surfaces only a small fraction of the total energy Eo in the drill in each cycle immediately preceding irnpact is utilized to do useful work. The majority of the energy, neglecting losses due to damping and impacts with the sides of the bore, remains in the drill and is functional only in reducing the work load on the powered winch in relifting the drill to the dropping position for the next cycle.

Assuming that the overall weight of a drill embodying the teachings of the instant invention has the same weight W as a conventional solid bar drill and that R denotes the weight of the bar assembly divided by the weight of the bit assembly (the weight of the spring is small enough by comparison to be neglected), it follows that ina typical drilling operation, optimal results are realized with R exceeding four. Let u1 as previously defined be the velocity of the bit assembly immediately preceding its first impact as depicted in FIG. 3. Let u2, ua and a4 denote its velocities immediately preceding its second, third, and fourth impacts as depicted, respectively, in FIGS. 5, 7, and 9. If m denotes the mass of the bit assembly, the energy Ec delivered to the ground by a weight equivalent conventional solid bar drill is given by the formula:

In the drilling action as depicted in FIGS. 3 to 11, the amounts of energy delivered during the 1st, 2nd, 3rd and 4th impacts with the bottom of the bore are, respectively Thus, the total energy Eph delivered is given by the formula:

If, in general, there are n impacts with the bottom of the bore, then the energy delivered is given by the formula:

Assuming that the collision between the end 51 of bar 32 and the end 50 of the stem 49 is performed under perfect elastic conditions, the successive velocity magnitudes are readily computed. In general velocities u2 and us will substantially exceed u1 with subsequent velocities being of decreasing magnitudes. Carrying out these calculations with k chosen so as to reflect rebound velocities for reasonably hard rock, for drill designs incorporating an appropriately chosen weight ratio between the bar assembly and the bit assembly and properly chosen spring compressions, the ratio Eph/EC will exceed two. This indicates the potential possibility of obtaining a better than 100% increased drilling eciency with the percussion hammer of the present invention as compared to conventional equipment.

Let El* denote the energy left in the drill subsequent to the fourth impact as depicted in FIG. 9. This quantity can be easily computed by considering the velocities of the bar and bit assemblies immediately subsequent to the fourth impact. E' has already been defined as the energy left in an equivalent conventional solid bar drill. The Law of Conservation of Energy, neglecting damping and other second order losses, requires that Hence, since in general Eph is larger than Ec, it follows that El* must be smaller than E. An estimate of the added energy which must be drawn from the powered Winch in relifting the drill to dropping position is given by the difference El-Ei.

The quantity of the added energy required is a minimum when the vibrations of the drill bit are in resonance With the cycle of lifting and dropping the drill by the rig, that is, when a whole number of impacts of the bit under the action of the spring 39 are executed each time the drill is raised and dropped.

As drilling proceeds, such as for a well, earth fluids may be encountered and it is necessary to prevent them from -fouling the moving parts of the device. Especially important is to keep foreign matter from entering the space 53 in the tubular section 34 above the stem 41 because the presence of such foreign matter wouldsprevent the solid elastic impact on the top of the stem against the bottom of the bar 32. In the absence of an effective seal between the slide 44 and the tubular shell 34, this undesirable condition may be avoided by so proportioning the volume of air space in the tubular shell above the top of the stern 41 in relation to the volume of air space between the bottom of the socket 36 and the top of the stem 41 so that air trapped will become compressed by the entrance of some fluid and exert sufficient pressure to prevent an excessive amount of fluid from entering on much the same principle as a bell jar submerged in a body of water. For `operating under depths of water up to about 200 feet, for example, the volume of the latter should be about l() times the former.

Having thus described my invention, I claim:

1. A percussion hammer drill comprising -an elongated rigid bar of substantially large weight, a drill bit carrier of relatively small weight, means supporting the carrier on the bar for longitudinal reciprocal Vmovement relative thereto, and a spring urging the carrier to a protracted position relative to the bar, said carrier and bar being disposed relative to each other -to mutually impact when the carrier is retracted a given distance from its protracted position against the action of the spring.

2.v A percussion hammer drill comprising an elongated rigid bar of substantially large weight, a hollow tubular member having one end thereof `secured to the bar, a drill bit carrier of relatively small weight mounted on the opposite end of the tubular member for longitudinal reciprocal movement therein, a coil spring within the tubular `member between the bar and carrier to urge the carrier to a protracted position, said carrier and bar being disposed relative to each other tol mutually impact when the carrier is retracted a given distance within the tubular member from its protracted position against the action lof the spring.

3. A percussion hammer drill comprising an elongated rigid bar of substantially large weight adapted to be disposed in a vertical position and to be alternately hoisted and dropped over a surface to be broken, a dn'll bit and a drill bit carrier on the bottom of the bar, said bit and carrier having la combined weight relatively smaller than the weight of the bar, means supporting thebit and carrier on the bar for axial reciprocation between a protracted position and a retracted position, means resiliently urging the bit to the protracted position, said carrier and bar ybeing disposed relative to each other to mutually impact when 4the carrier and bit are retracted a given distance from the said protracted position against the action of the spring.

4. A percussion hammer drill comprising `an elongated rigid bar having a substantially large weight adapted t-o be disposed in a vertical position and to be alternately hoisted and dropped over a surface to be broken, a drill bit on the bottom of the bar, said bit having a weight substantially less than the weight of the bar, means supporting the bit on the bar for longitudinal freciprocation between the protracted and retracted positions, means resiliently urging the bit to the protracted position, and abutment means between the bit and the bar for limiting the protracted position of the bit.

5. A percussion hammer drill comprising an elongate-d rigid bar having a substantially large weight adapted to be disposed in a vertical position and to be alternately hoisted and dropped over a surface to be broken, a drill bit on the bottom of the bar, said bit having a weight substantially less than the weight of the bar, means supporting the bit on the bar for longitudinal reciprocation between `the protracted and retracted positions, a coil spring for resiliently urging the bit to the protracted position, and :abutment means between the bit and bar for limiting the protracted position of the bit.

6. A percussion hammer drill comprising an elongated bar having a substantially large weight, said bar being adapted to be disposed in a vertical position and to be alternately hoisted and dropped over a surface to be broken, a drill bit on the bottom of the bar, said bit having a relatively small weight, a tubular section between the bar and the bit, said tubular section having a confined space, a slide member disposed for reciproeation within said space between positions of protraction and retraction, a coil spring within said space between the bar and the slide urging the slide member to its protracted position, elastic abutment means between the slide and bar for limiting the retraction of the slide, a socket connected to the bottom of the tubular member, a drill bit reciprocally mounted .on the socket, and means connecting the drill bit with said slide member for comovement therewith.

7. A percussion hammer drill as defined by claim 6 and a fluid seal between said slide and tubular section.

8. A percussion hammer drill comprising an elongated bar having a substantially large Weight, said bar being adapted to be disposed in a vertical position and -to be alternately hoisted and dropped over a Surface -to be broken, a drill bit on the bottom of the bar, said bit having a relatively small weight, a tubular section between the bar and the bit, said tubular section having a confined space, a slide member disposed for reciprocation within said space between positions of protraction and retraction, a coil spring within said space between the bar and the slide urging the slide member to its protracted position, elastic abutment means between the slide and bar for limiting the retraction of the slide, a socket connected to the bottom of the tubular member, said socket having a wall at its lupper end, said wall having an aperture therethrough, a shaft integral with said bit, said shaft projecting through said aperture and being connected to said slide.

9. A percussion hammer drill as dehned by claim 3 in combination with means for raising and lowering the drill periodically.

1th. The method of operating a percussion hammer having a drill bit adapted to vibrate between fixed limits of retraction .and protraction, said method comprising raising and lowering the hammer cyclically in a period substantially equal to the periods of a Whole number of vibrations of the bit.

11. rlhe method of operating a percussion hammer having a drill bit adapted to vibrate between Xed limits of retraction and protraction, said method comprising raising and lowering the hammer cyclically in resonance with the vibrations of the bit.

References Cited UNITED STATES PATENTS 527,237 10/1894 Downie 173-81 1,102,652 7/1914 Gibb et al. 173-91 1,892,517 12/1932 Pennington 173--132 1,896,992 2/1933 Agren 173-133 2,742,266 4/ 1956 Voelkerding 173-91 FRED C. MATTERN, J R., Primary Examinez'. L. P. KESSLER, Assistant Examiner. 

10. THE METHOD OF OPERATING A PERCUSSION HAMMER HAVING A DRILL BIT ADAPTED TO VIBRATE BETWEEN FIXED LIMITS OF RETRACTION AND PROTRACTION, SAID METHOD COMPRISING RAISING AND LOWERING THE HAMMER CYCLICALLY ON A PERIOD 